This invention relates to a cross-axis cutting assembly of a selective cutting machine.
Such an assembly typically has two cutting heads supported by a boom, the cutting heads being driven by a shaft directed transversely to the boom. Spray nozzles are arranged on the cutting heads, the nozzles being connected, via pressure water ducts formed in the cutting heads and via rotary arrangements, to an external high pressure water supply line (Journal "Gluckauf" 1985, page 1206).
Selective cutting machines are used to advance tunnels, galleries and the like, including galleries driven through rock and seams in underground mines, and for the winning of mineral deposits. To abate the dust formed during cutting operations, to cool the cutting tools, and to avoid methane ignition in fire-damp mines, it is necessary to spray the working region with water under pressure. Generally, internal spraying is adopted, that is to say water under pressure is supplied from the exterior, and is introduced into each of the cutting heads via a rotary arrangement. The pressurised water is then fed to spray nozzles arranged on the periphery of the cutting heads via pressure water ducts formed in the cutting heads. A cutting head having such internally-fed spray nozzles is generally equipped with means for controlling the supply of pressurised water which ensures that water is fed only to the spray nozzles located in the region of the cutting head whose cutters are actually cutting (see DE-OS No. 28 10 982 and EP-PS No. 10 534).
With selective cutting machines used in hazardous mines, it is becoming more and more necessary to spray water intentionally into the working region of the individual cutters, that is to say in the cutting tracks thereof, in such a way that effective abatement of dust and particularly effective cooling of the cutting zones is achieved, whilst ignition of issuing methane gas by spark formation in the cutting zone is also avoided. With this process, working pressures of the order of at least 100 to 200 bar, and frequently even 300 bar and higher are required for the spray water. Considerable sealing problems arise with such high working pressures if the rotary arrangement is arranged on the roller hub or the drive shaft of a cutting head. The sealing problems are greater, the greater the diameter of the shaft or hub of the cutting head provided with the rotary arrangement. When using a planetary gear positioned within a cutting head, the shaft diameter to be sealed by the rotary arrangement is not excessively large so that, at least if the working pressures of the spray water are not too high, the sealing problems can generally be solved. The conditions may be different if a mitre gear is provided instead of the planetary gear. The use of a mitre gear has the substantial advantage over a planetary gear that a cutting head can have reduced diameter. On the other hand, however, considerable problems arise in providing the resultant large diameter drive shaft of a cutting head with a rotary arrangement for the supply of pressurised water which acts as a reliable seal for a prolonged operating time under the necessarily high pressures of the spray water.
The object of the invention is, therefore, to provide a cross-axis cutting assembly whose cutting heads have internally-fed spray nozzles, which assembly avoids using rotary arrangements of large diameter, whilst ensuring reliable introduction of the high pressure water into the cutting heads and through the cutting heads to the spray nozzles.